1. Field of the Invention
The present invention generally relates to a method of recording data in a multilayered recordable optical recording medium, a recording and reproducing apparatus for recording the data in the recording medium, and the recording medium.
2. Description of the Related Art
Recently, individual users have handled audio data, image data, and video data whose capacity is large. Meanwhile, a large capacity HD (hard disk) has been developed; however, the recording capacity is not sufficient, and even recording media such as a CD (compact disk), a DVD (digital versatile disk), and a medium using a blue laser have not had sufficient capacity.
In order to increase the recording capacity, a multilayered optical recording medium has been developed. The multilayered optical recording medium is formed by stacking plural layers on a substrate.
In a recording apparatus using the multilayered optical recording medium, a suitable pulse width, a suitable pulse strength, a suitable pulse shape, a suitable recording strategy, and so on are determined by test recording, and information (data) is recorded in the recording medium after the test recording.
When information is recorded in an optical recording medium, a process called calibration is generally executed in which calibration test recording is executed before actual recording, signal quality at a part where the test recording is applied is investigated, and an optimum value of laser beam intensity to be used is obtained. In recordable optical media such as a CD type medium and a DVD type medium, an area where the test recording is applied is at a most internal area of the disk, and the area is called a PCA (power calibration area). The above process is called OPC (optimum power control). In the present invention, instead of using the PCA, a test recording area is used.
As for the test recording, an existing β method and an existing γ method can be used.
When information is recorded in the multilayered optical recording medium, a laser beam reaches recording layers other than a nearest recording layer via the nearest recording layer, translucent reflection layers, adhesive films, intermediate films, and so on, viewed from a laser beam irradiating side.
FIG. 29 is a schematic diagram showing a status difference among second recording layers when information is recorded in a first recording layer. In FIG. 29, the second recording layer is the nearest recording layer to a laser beam, and the information is desired to be recorded in a first recording layer. In addition, in FIG. 29, a part where horizontal lines exist is an information recorded part.
In FIG. 29 (a), no information has been recorded in the second recording layer. In FIG. 29 (b), information has been recorded in all parts of the second recording layer where a laser beam is being irradiated. In FIGS. 29 (c) and (d), information has been recorded in a part of the second recording layer where a laser beam is being irradiated. In FIG. 29 (e), information has not been recorded in a part of the second recording layer where a laser beam is being irradiated. In FIG. 29 (f), information has been recorded in a part of the second recording layer where a laser beam is being irradiated.
When information is recorded in the first recording layer, the transmission rate of the laser beam to the first recording layer is changed depending on whether information has been recorded in the second recording layer.
For example, in FIG. 29, depending on the information recorded statuses in the second recording layer, the transmission rate of the laser beam to the first recording layer is greatly changed. That is, suitable recording conditions, for example, sensitivity of the laser beam on the first recording layer, are different among the information recorded statuses in the second recording layer.
In order to solve the above problem, Patent Document 1 discloses a multilayered optical disk having stacked plural recording layers. In the multilayered optical disk, a laser beam is irradiated from a specified surface and information is recorded in the plural recording layers and the recorded information is reproduced from the plural recording layers. In the disk, information is recorded in the recording layers starting at a recording layer nearest to the laser beam in order.
The recording layer is divided into plural zones in the diameter direction and the circumferential direction of the disk, flags showing the information recorded statuses (information recorded status flags) of the corresponding plural zones are recorded in a predetermined area, and a power value of the laser beam is controlled based on detection of the flag.
However, when information is sequentially recorded in the plural layers starting at the recording nearest the laser beam irradiating side in order, all the recording layers to which the laser beam is transmitted must provide the corresponding information recorded status flags. In addition, when the power value of the laser beam is determined at the time of recording and reproducing information, all of the information recorded status flags must be considered. That is, very complicated information management is required and detailed power control is required.
Especially, when the number of the recording layers is increased, the number of the information recorded status flags to be managed is increased; therefore, Patent Document 1 may not be effectively used in a multilayered optical recording medium in which the number of the recording layers is three or more.
In addition, as shown in FIGS. 29 (e) and (f), even if the information has been recorded in the second recording layer, an information unrecorded part may exist in the second recording layer due to, for example, defects.
In addition, the transmission rate of the laser beam is obviously different between the statuses shown in FIGS. 29 (b) and (e); however, the statuses may be handled as the same statuses. Consequently, suitable information recording in the first recording layer may not be executable.
In a case where information is recorded in the first recording layer through the second recording layer, only when defective recording does not exist in the second recording layer, the information can be recorded in the first recording layer. The defective recording is generated when the transmission rate is changed or dispersed.
Further, in Patent Document 1, as the recorded status flag, there are only two types of flags in the second recording layer positioned in front of the first recording layer where information is to be recorded. One of the flags shows that no information has been recorded in the second recording layer, and the other of the flags shows that a certifying process has been applied to the second recording layer or information has been fully recorded in the second recording layer. Consequently, optimum recording power or optimum reproducing power is not determined to the first recording layer.
That is, even if it is said that information has been recorded in a recording layer, the recorded status in the recording layer always has fluctuations depending on the position of the recording layer in the disk due to unevenness thickness of the recording layer, dispersion, tilt, decentration (not being concentric) of the recording layers in the disk, or a defect on the substrate of the disk or the recording layer.
That is, due to the fluctuations of the recorded status of the recording layer, the transmission rate of the laser beam fluctuates in a recording layer where the information is to be recorded, and the suitable recording conditions are changed in the recording layer where the information is to be recorded via a recording layer where information has been recorded. Consequently, the recording conditions in the recording layer where the information is to be recorded may not be optimum by using only the recorded status of the recording layer where the information has been recorded positioned in front of the recording layer where the information is to be recorded.
FIG. 30 is a schematic diagram showing zones when a recording area of a recording layer is divided into plural zones.
In Patent Document 1, as shown in FIG. 30, the recorded statuses of the first and second recording layers are managed in zones divided by the same corresponding distances from the center of the disk in the radius direction. In addition, in order to make the management of the recorded statuses easy, the width of the zone is greater than the diameter of the laser beam on the second recording layer, and the number of the flags to be managed is decreased.
For example, in a case where the width of each zone is determined as shown in FIG. 30, when information is recorded in a zone B1 of the first recording layer and a laser beam “in” is irradiated at an inner circumferential end of the zone B1 and a laser beam “out” is irradiated at an outer circumferential end of the zone B1, the zones of the second recording layer on which zones the recorded statuses are to be managed can be limited to three zones A2, B2, and C2.
However, in the zones A2, B2, and C2, having no dispersion of recording quality and no unrecorded part are not assured. Therefore, when the zone is made to be wider, the reliability of the suitable recording conditions in the first recording layer is lowered.
In order to make the reliability of the suitable recording conditions in the first recording layer high, the width of the zone is narrowed; however, the number of the zones to be managed is increased and this is not practical.
Patent Document 2 discloses an information recording method in an optical information recording medium. The medium provides two or more information recording layers, and a recording power test area for checking recording power is provided at an area other than an information recording area (user data recording area). When the number of the information recording layers is “n”, the number of the recording power test areas is “n−1” or more, and one recording power test area is allocated to each information recording layer. Then information is recorded in an optical information recording medium by a laser beam by determining whether the medium has one of three statuses of a lowest transmission rate of the laser beam, a highest transmission rate of the laser beam, and both of the transmission rates of the laser beam. That is, the power test is applied to the above three statuses, the recording power is determined, and information is recorded in the information recording area based on the determined recording power.
However, when the number of the layers is increased, the number of combinations of the recorded statuses of the layers is increased, and the capacity of the power test areas may not be sufficient.
That is, the combinations of the recorded statuses must be obtained in the recording layers positioned in front of a recording layer where the power test is to be applied. In order to obtain high reliability of the power test, a width having a certain size or more is required in the front-positioned recording layers in the radius direction; however, since a sufficient width cannot be obtained, sufficient capacity of the power test area cannot be obtained.
When a sufficient width of the power test area cannot be obtained in the radius direction in the combinations of the recorded statuses of the front-positioned recording layers, the reliability of the power test is greatly lowered.
When the combinations of the recorded statuses of the recording layers are in a circumferential direction of the recording medium, a scheme for separating the combinations of the recorded statuses may be required. That is, the information of the scheme must be in a pre-pit and a wobble of the recording medium.
FIG. 31 is a schematic diagram in which combinations of recorded statuses of (K+1) and (K+2) layers are in a circumferential direction of a recording medium when information is recorded in a K layer behind the (K+1) and (K+2) layers.
As shown in FIG. 31, when combinations of recorded statuses of the (K+1) layer and the (K+2) layer are recorded in divided areas A through H in the circumferential direction of the recording medium and suitable recording conditions in the K layer are obtained in the divided areas A through H in test recording of the K layer, information can be recorded in the K layer with the suitable recording conditions based on the recorded statuses of the layers (K+1) and (K+2).
However, when the recorded statuses of the (K+1) and (K+2) layers are not ideal, the suitable recording conditions with high reliability cannot be obtained in the K layer. In the ideal status, the recorded statuses do not have an unrecorded area with a defect, and the recorded area does not have fluctuations and/or dispersions of the transmission rate of a laser beam.
FIG. 32 is a schematic diagram showing a difference between recorded statuses in the (K+1) layer when information is being recorded in the K layer. In FIG. 32 (a), a laser beam is transmitted through a recorded area of the (K+1) layer, and in FIG. 32 (b), a part of the laser beam is transmitted through the recorded area of the (K+1) layer.
The suitable recording conditions in the K layer are different between statuses shown in FIGS. 32 (a) and (b); however, Patent Document 2 does not teach how to handle the difference.
Patent Document 3 discloses an optical information recording medium. The medium provides two of a first through Nth recording layers (N is an integer of 2 or more) disposed in order from both of the laser beam irradiating side and the laser beam irradiating opposite direction. When a laser beam is irradiated on any one of the first through Nth recording layers from one of the directions, information is recorded in a recording layer or is reproduced from a recorded recording layer. At least any one of the first through Nth recording layers provides a correction information recording section. Correction information for correcting intensity of the laser beam is recorded in the correction information recording section based on changes of transmission rates of the laser beam between an unrecorded status and a recorded status in the second through nth recording layers.
Each of the first through Nth recording layers provides a test recording area for executing test recording and an information recording area for recording user data. The test recording area of a Kth recording layer (K is an integer satisfying “1≦K≦N−1”) is arranged at a position different from positions of the test recording area and the information recording area of the (K+1)th through the Nth recording layers in the radius direction of the recording medium.
In Patent Document 3, a pulse condition of a laser beam including the intensity of the laser beam is determined by using a result of the test recording and the correction information. With this, information is to be recorded with high reliability.
Similar to the present invention, in Patent Document 3, when suitable recording conditions are obtained in the Kth layer, layers in front of the Kth layer are caused to be in an unrecorded status, and the reliability of the OPC of the Kth layer is made to be high. However, Patent Document 3 has the following problems.
FIG. 33 is a schematic diagram showing a first case where decentration exists between recording layers of a recording medium. FIG. 34 is a schematic diagram showing a second case where decentration exists between recording layers of a recording medium. In FIGS. 33 and 34, a black part in the K and (k+1) layers is a test recording area.
For example, when a test recording area of a K layer is shifted from a test recording area of a (K+1) layer in the radius direction of a recording medium, the reliability of the OPC in the K layer can be high. However, when the number of the recording layers is increased, a wider test recording area is required in the recording medium, and the recording capacity of the recording medium may be lowered.
As shown in FIG. 33 (a), when a test recording area of a K layer is shifted from a test recording area of a (K+1) layer in the radius direction of a recording medium, actually, a decentration and/or circularity (not being circular) amount is different between the K layer and the (K+1) layer. Therefore, as shown in FIG. 33 (b), the test recording area of the K layer may be overlapped by the test recording area of the (K+1) layer, and the reliability of the OPC may be lowered.
In order to prevent the overlap of the test recording area of the K layer on the test recording area of the (K+1) layer, as shown in FIG. 34, the test recording area of the K layer must be at a position away from the test recording area of the (K+1) layer by an amount of the decentration (generally, approximately 10 to 30 μm). However, in this case, the test recording area in the recording medium is remarkably increased and the recording capacity in the recording medium may be lowered.
In Patent Document 3, the suitable recording conditions in the K layer are obtained from the correction information in the combinations of the recorded statuses of the layers in front of the K layer. However, actually, the test recording cannot be executed on all the combinations; therefore, high recording reliability on the K layer may not be obtained.
When information is actually recorded in the K layer, as shown in FIG. 29, the recorded statuses of the layers in front of the K layer are different from each other. The suitable recording conditions of the K layer cannot be determined in all the recorded statuses of the layers in front of the K layer. Consequently, the recording reliability in the K layer may not be sufficient. The suitable recording conditions in the K layer based on the test recording can be obtained in the cases shown in FIG. 29 (a) and FIG. 29 (b) in which the suitable recording conditions can be obtained from the correction information.
In Patent Document 4, the recording order among the recording layers is determined. That is, after recording information in a recording layer at a front side, information is recorded in a recording layer positioned at a back side. However, similar to Patent Document 1, the recorded statuses of the recording layers at the front side may be different from each other as shown in FIG. 29. Therefore, when the number of the recording layers at the front side is increased, the suitable recording conditions in the recording layer where information is to be recorded cannot be determined by conventional OPC.
In Patent Documents 5 and 6, the recording order among the recording layers is determined. When information is recorded in a recording layer at a back side after recording information in a recording layer at a front side, the information recording in the recording layer at the front side influences the information recording in the recording layer at the back side. Therefore, after recording information in the recording layer at the back side, the information is recorded in the recording layer at the front side.
In Patent Documents 5 and 6, similar to the present invention, the recording order among the recording layers is determined. However, a specific method for determining the optimum recording power in each recording layer is not disclosed.
In Patent Document 7, a dummy signal has been recorded in a recording layer at a front side beforehand.
However, similar to Patent Document 1, this is effective when the recorded statuses of the recording layers are ideal. In the ideal situation, the recorded statuses do not have an unrecorded area duet to defects, and the recorded area does not have fluctuations and/or dispersions of the transmission rate of a laser beam. That is, it is difficult to realize this in an actual situation.    [Patent Document 1] Japanese Laid-Open Patent Application No. 2000-293947    [Patent Document 2] Japanese Laid-Open Patent Application No. 2003-22532    [Patent Document 3] Japanese Laid-Open Patent Application No. 2004-171740    [Patent Document 4] Japanese Laid-Open Patent Application No. 2000-285469    [Patent Document 5] Japanese Laid-Open Patent Application No. 10-269575    [Patent Document 6] Japanese Laid-Open Patent Application No. 3-157816    [Patent Document 7] Japanese Laid-Open Patent Application No. 2000-36130